This disclosure relates to an engine gas-oil separator provided in a head cover for separating oil contents in blow-by gases that are recirculated to an air intake system of a normally aspirated engine.
Many gas-oil separation devices exist for separating oil mist from crank case gases. The crank case gases are recirculated back to an intake manifold of the engine for improved emissions. The gas-oil separation typically occurs between the intake manifold, which is usually under negative pressure, and the crank case, which is usually near atmospheric pressure. In a naturally aspirated engine, the crank case maintains near-atmospheric pressure condition because fresh air is supplied from outside the engine, usually through an air intake tube. The fresh air mixes with combustion gases that have leaked past the piston rings (hereinafter referred to as blow-by gases). The resulting mixture is drawn through a positive crank case ventilation (PCV) chamber where oil mist is separated from the blow-by gases. Ideally, the separated oil drains back to an oil sump while the blow-by gases are drawn into the intake manifold.
Many devices exist for separating oil from blow-by gases in the PCV chamber, such as foam blocks, rotating elements built into cam shafts, or complex systems of baffles. Problems arise, however, when the crank case pressure is greater than the PCV chamber intake flow pressure such as during high load conditions. Blow-by gases can be forced out of the crank case backwards through the path in which fresh air typically enters into the PCV chamber. This situation can be described as back-flow, where the excessive blow-by gases that are not drawn in by the PCV chamber are blown back through the fresh air intake path. This back-flow condition can carry oil entrained in the blow-by gases, and this oil can collect in the intake manifold, which can then negatively impact combustion, emissions and marketability.